The utility model discloses a magnetically-controlled electric reactor and belongs to oil immersed type reactors. The magnetically-controlled electric reactor comprises an oil tank and a control box, wherein the control box is fixed to the top of the oil tank. A radiator is arranged outside the oil tank wall, and a magnetically-controlled electric reactor body is arranged in the oil tank. The magnetically-controlled electric reactor body comprises a core limb, a magnetic exciting coil and a magnetic control coil. A magnetic exciting control portion comprises an isolating variable circuit, a monitoring and protecting circuit, a control circuit, a control signal photovoltaic converting circuit, an optical fiber transmission circuit and an optical receiving circuit which are arranged in the control box. The magnetic exciting control portion further comprises a rectifying circuit which is mainly formed by a thyristor arranged on the outer wall of the oil tank. Due to the fact that magnetic control electric signals are converted into optical signals and transmitted by optical fibers, the control signals can be completely separated from high-voltage electromagnetic interference signals and radio-frequency interference signals of the thyristor. Thus, the interference resistance is improved. Due to the facts that an oil channel is formed in the core limb and the thyristor is arranged on the outer wall of the oil tank, the radiating efficiency is high, and the whole service life of the reactor is prolonged.